Planar technology to fabricate semiconductor devices is now important for progress in electronics. Such a type of a conventional method for fabricating a semiconductor device comprises the steps of forming an insulating layer on a main surface of a semiconductor substrate, fluidizing the insulating layer by heating to smooth the surface thereof, opening contact holes in desired points of the insulating layer, and forming conductor contacts on the contact holes for interconnection.
In the conventional method for fabricating a semiconductor device, however, there is a disadvantage in that a thickness of the insulating layer is not uniform, so that over-etching of the insulating layer can occur in a patterning step of the contact holes, which causes damage to the surface of the semiconductor substrate. Moreover, some of the contact holes are quite deep and have steep side walls in the ununified insulating layer, so that the step coverage is poor and cracks of the conductor contacts can develop.